The just-noticeable difference is the minimal change that can occur in a stimulus to just barely be detected by the observer. In this case, the stimulus is the brightness of light. As for the other answer choices, the absolute threshold is the minimal intensity at which a stimulus can barely be detected. This concept is similar to the just-noticeable difference but has to do with detection of existence, rather than detection of change. Sensory adaptation refers to how an observer becomes less sensitive to a stimulus over time. Signal detection states that an observer's response to a stimulus depends on both their sensitivity and their decision criterion. Transduction is the process of physical signals being converted to neural signals.